*4.1. Dependence of Growth Kinetics and Microstructure on the Gas Environment*

The coating deposition kinetics was dependent on the composition of the sputtering atmosphere. The introduction of N2 (10 sccm) into Ar flow resulted in an 11% increase in growth rate (coating 3, Table 2), whereas the introduction of a similar amount of C2H4 slightly decreased the growth rate. Both nitrogen and carbon formed related phases in the coatings, suggesting that the difference in growth rates arises from different ionization behavior of N2 and C2H4 and higher scattering of atoms of sputtered material by C2H4 molecules (Table 1). The decrease in the size of h-TaSi2 crystallites and the amorphization of coatings deposited in a reactive atmosphere is associated with the formation of new TaN and TaC phases, which apparently interrupt the growth of h-TaSi2 crystallites. Reactive sputtering was instrumental in eliminating the unwanted columnar structures in the coatings (Figure 2). Columnar structures are known to adversely affect the mechanical and tribological properties of coatings, as well as their oxidation resistance [34,35].
